This invention relates to a composite-machining machine tool capable of carrying out a machining center operation and a hobbing operation in addition to a turning operation.
Recently, in order to carrying out various kinds of machinings with a single machine tool, there have been developed composite-machining machine tools which can carry out a machining center operation in addition to a turning operation. The Applicant of the present invention developed a composite-machining machine tool capable of efficiently carrying out various kinds of machinings including milling, drilling, tapping and etc., and filed a patent application for it (Japanese Laid-Open Patent Application No. 63-74534). The Applicant also developed a mechanism by which a workpiece can be automatically attached and detached relative to this kind of machine tool, using a pallet, and filed a patent application for it (Japanese Laid-Open Patent Application No. 63-212432). However, although such composite-machining machine tools can carry out milling, drilling, tapping and etc., they are not provided with a mechanism for generating gear teeth by hobbing, and thus the generation of the gear teeth could not be done. Namely, in order to generate the gear teeth by hobbing, the lead angle of the hobbing must be delicately (for example, with a precision of about 0.001 degrees) positioned depending on the diameter of the gear to be machined, and there has heretofore not existed any composite-machining machine tool provided with a mechanism for effecting such precise positioning, and therefore the hobbing could not be carried out.
On the other hand, most of conventional hobbing machines are designed to perform only a hobbing operation, and with respect to composite machining effected by the hobbing machine, a turning operation can be carried out at best in addition to the hobbing operation.
Therefore, conventionally, in order to machine a workpiece to be subjected to gear formation, machinings, such as turning, milling, drilling, tapping and so on, are applied to those portions of the workpiece except for the gear portion, using the composite-machining machine tool as disclosed in the above-mentioned publications, and then the workpiece is set in a gear formation machine such as a hobbing machine, thereby machining the gear portion. Thus, the machining of at least two steps must be done, and much labor and time have been required for the machining.